This a fixture for testing circuit boards and, in particular, a fixture including a plate having a registration pattern thereon.
Fixtures for testing printed circuit boards are common in the art and include drilled test points and tooling locations based on design criteria to correlate with the printed circuit board to be tested. The problem of tooling to pattern misregistration in test fixtures is a common problem in testing procedures. Misregistration occurs when the test points of a circuit board pattern do not register with the test points of the fixture designed according to CAD or Gerber design criteria, in conjunction with the multiple stage drilling operations that are required. Due to the continued miniaturization of circuit boards and due to the material growth of the circuit boards or shrinkage during processing, misregistration has become even more commonplace and detrimental to testing procedures. It is necessary to correct misregistration to avoid errors or opens. Under such misregistration, it is possible to have a network which is actually error free. However, due to the misregistration, pseudofaults will occur indicating that the circuit board is erred. This results in time-consuming, error-prone pseudofaults that can severely affect the test times and the costly "escapes." In prior fixtures misregistration was overcome by use of micrometers and building specialized fixtures to correlate with the printed circuit board to be tested. Such procedures were very costly and timely. Accordingly, there is needed a device which allows for the correction of the misregistration quickly and inexpensively.
It is therefore an object of the present invention to provide a testing fixture having a means for registering the fixture quickly and easily to a circuit board.